mmc: sdhci-pltfm: move devm_ioremap_resource() up

Call devm_ioremap_resource() right after platform_get_resource().
This saves the error check of platform_get_resource() because
devm_ioremap_resource() checks if the given resource is NULL.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>